Composite slab casting form

ABSTRACT

A form for casting prestressed concrete slabs which are intended to provide an integral, finished ceiling when installed. The base or pan of the form is constructed as a relatively heavy plate to resist deflection, particularly transversely of a form, when the form is filled with concrete. The upper surface of the pan is machined with great accuracy to provide a pair of notches each having straight, flat walls extending longitudinally of the pan. A pair of side plates are machined to provide each with a side leg joined by a smoothly curved section to an inwardly extending base leg, and the side plates are positioned in the notches. Aligning forces are applied to the side plates in the direction of the outer side walls and bottom walls of the notches to straighten the side plates and pan, if necessary, and the plates are then fixed in the pan by welding. When the side plates are thus assembled on the pan the base legs extend inwardly of the form from the curved sections and the inner ends of the base legs, together with inner side walls of the notches, define cavities which are filled with a welding material. The welding material is then ground flat to provide a smooth transition surface between the upper surface of the pan and the upper surface of the base leg. Because the base legs extend a distance inwardly of the form from the curved sections, the welding material in the cavities may be ground without gouging the curved connecting sections or other surfaces of the form.

UnitedStat es Patent [191 Wise COMPOSITE SLAB CASTING FORM [75] Inventor: Mark J. Wise, Brookville, Ohio [73] Assignee: The Flexicore C0., Inc., Dayton,

. Ohio [22] Filed: Dec. '13, 1971 [21] Appl. No.: 207,190

[52] US. Cl 249/50, 249/99, 287/l89.36 B

[51] Int. Cl B28b 7/22 [58] Field of Search 249/50; 164/137, 342; 287/2092 D, 189.36 B; 245/50, 99

[56] References Cited UNITED STATES PATENTS 3,305,909 2/1967 Wise et a]. 425/440 2,163,209 6/1939 Pungel .1. 287/l89.36 B 3,023,477 3/1962 Smith et al.... 249/50 3,348,279 10/1967 Shoe 425/440 2,591,858 4/l952 Ostendorf 164/342 X 687,740 12/1901 French 287/2092 D 2,376,574 5/1945 Collins 287/l89.36 B X Primary Examiner-Robert D. Baldwin Attorney, Agent, or F irm-Biebel, French & Bugg 57 ABSTRACT A form for. casting prestressed concrete slabs which 11 3,790,120 Feb. 5, 1974 are intended to provide an integral, finished ceiling when installed. The base or panof the form is constructed as a relatively heavy plate to resist deflection, particularly transversely of a form, when the form is filled with concrete. The upper surface of the pan is machined with great accuracy to provide a pair of notches each having straight, flat walls extending longitudinally of the pan. A pair of side plates are machined to provide each with a side leg joined by a smoothly curved section to an inwardly extending base leg, and the side plates are positioned in the notches. Aligning forces are applied to the side plates in the direction of the outer side walls and bottom walls of the notches to straighten the side plates and pan, if necessary, and the plates are then fixed in the pan by welding. When the side plates are thus assembled on the pan the base legs extend inwardly of the form from the curved sections and the inner ends of the base legs, together with inner side walls of the notches, define cavities which are filled with a welding material. The welding material is then ground flat to provide a smooth transition surface between the upper surface of the pan and the upper surface of the base leg. Because the base legs extend a distance inwardly of the form from the curved sections, the welding material in the cavities may be ground without gouging the curved connecting sections or other surfaces of the form.

17 Claims, 4 Drawing Figures COMPOSITE SLAB CASTING FORM BACKGROUND OF THE INVENTION Precast concrete slabs of the type shown, for example, in U.S. Pat. No. 2,299,070, have heretofore been manufactured using a variety of different types of casting equipment. One type that is used is a form of, perhaps 60 feet in length and some two feet in width, provided with inwardly projecting portions for defining grout keyways in the slabs. A form of this construction is shown in U.S. Pat. No. 3,023,477, and as described therein, this form is manufactured, essentially, from a single piece of steel of high tensile strength thay may be flexed in a special stripping fixture to permit the cured concrete slab to be removed from the form.

While this type of form has enjoyed widespread commercial success, there appear to be limitations on the width of a slab to be manufactured in forms of this design. Thus, in forms of increased width some method must be provided for resisting the increased transverse 1 deflection forces generated by the increased weight of concrete.

One apparent solution would be to make the form of a thicker sheet of steel. However, above a certain thickness it becomes very difficult to work the sheet material to form the smoothly curved bends between the bottom and side walls of the form.

Another apparent solution is to construct the form of separate base and side wall plates joined to each other by welding and provide a fillet of welding material at the interior corners defined by the juncture of the base and side wall plates and thereafter machine this fillet to provide the desired, smoothly curved interconnecting surface. It has been found, however, that it is extremely difficult to grind the welding material without gouging or undercutting adjacent surfaces of the form. As a result, the interior surfaces of the form are gouged, causing blemishes in the pan which transfer to the concrete, ruining the smooth, finished ceiling effect desired. Additionally, if such gouges form undercut portions in the vertical walls of the form, difficulties in removing the slab from the form and chipping may be encountered.

Consideration has also been given to providing reenforcing beams or struts for the under surface of the form. Again, as a practical matter, this solution has proved unacceptable because it would interfere with movement of the form on wheeled or roller conveyors. While removable struts might be used, this would require separate parts which must be transported and installed, whether manually or mechanically.

SUMMARY OF THE INVENTION A composite form particularly adapted for casting relatively wide slabs is constructed in accordance with the present invention by utilizing a relatively thick, high strength steel plate as the base member and a pair of upstanding side plates secured to the base member. The thick base plate provides the increased resistance to transverse deflection necessary when constructing wider slabs and structurally assists in resisting prestressing forces applied to the form.

To provide the smoothly curved intersection between the bottom and side walls of the form, the side plates are machined to form an upwardly projecting'side leg, an inwardly extending base leg, and a smoothly curved radius section joining the base and side legs.

The base plate is provided with notches machined with great accuracy to provide straight, flat bottom, and

side walls extending longitudinally of the base plate in spaced parallel relationship to each other. The depth of the notch is equal .to the thickness of the base leg and the two longitudinally extending cavities formed by the inner ends of the base legs and the opposed surfaces of the notches in which they are received are filled with a welding material which is thereafter finished by grinding to provide a smooth transition surface between the upper face of the base plate and the upper surface of the base leg.

In this regard it will be noted that the base legs of the side plates have flat upper surfaces which extend inwardly into the form away from the smoothly curved intersection between the base and side legs. As a result, the weld material mentioned above is readily accessible for grinding or machining by conventional machine tools without the danger of gouging into the curved intersection. Thus, there are no portion which would cause blemishes in the slab surface, detracting from the smooth slab surface necessary to provide a finished ceiling, nor undercuts in the vertical walls of the form which would interfere with slab removal and cause chipping of the slab.

Because the notches in the base plate or pan are ma chined with great accuracy and the side plates are quite rigid vertically, some straightening of the pan and side plates may take place during installation of the side plates. Thus, after the side plates are initially positioned in the notches, aligning forces are applied thereto against the bottom and outer side walls of the notches to bring opposing portions of the side plates into face to face contact with the bottom and outer side walls of the notch. The plates are then fixed in this aligned position by welding.

As noted above, the forms are designed to be flexed by a stripping fixture to remove the cured slabs therefrom. Because of this it is desirable to remove as little material as possible from the base plate when forming the notches therein to avoid weakening the plates any more than necessary. By forming the base legs relatively thin, the depth of the notches in the upper surface of the base plate which receive the base legs is kept at a minimum.

Cap members are preferably mounted on the top edges of the side plates and project outwardly of the form beyond the longitudinal edges of the pan. The cap members thus stiffen and reenforce the form, provide flanges for handling and prevent excess concrete screeded from the form from being deposited on the longitudinal edges of the pan.

BREIF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of the form of the present invention;

FIG. 2 is an end view of a side plate;

FIG. 3 is an exploded end view of a portion of the form; and

FIG. 4 is a view similar to FIG. 3 but showing the parts assembled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As seen in the drawings, a form 10 in accordance with the present invention includes a base or part 12 formed from a relatively thick, flat steel plate. In its upper surface 14 the plate 12 has machined therein with great accuracy a pair of spaced parallel longitudinally extending notches 16. Each notch 16 includes a straight, flat bottom wall 18 and straight, flat inner and outer side walls 20 and 22, respectively projecting substantially perpendicularly upwardly from the bottom wall to define a notch of substantially rectangular cross section.

The composite form also includes a pair of one piece, relatively thick, side plates 24. Each of these side plates 24, as best seen in FIG. 2 of the drawings, includes an outer face 26, an inner face 28 and top and bottom edges 30 and 32, respectively, extending substantially perpendicularly between the inner and outer faces.

The inner face 28 of each of the side plates has portions removed therefrom by machining or the like, as indicated by cross hatching 33, to define a base leg 34 having a lower surface coincident with the bottom edge 32 of the plate 24, an upper surface 36 extending substantially parallel to the lower surface, and an inner end 38 spaced from the outer face 26. Removing portions of the inner face of the side plate 24 also provides a side leg 40 having an inner surface 42 extending parallel to the outer face 26 and a smoothly curved radius portion 44 interconnecting the inner surface 42 and the upper surface 36 and having a radius of from five-eighths to one-fourth inch with an optimum of approximately three-eighths inch.

Additionally, it will generally be desirable, in removing a portion of the side plates, to form an inwardly projecting grout key forming protrusion 46. Although shown as a single continuous member it will be apparent that the grout key cavitiy defining protrusion might also be formed as a series of spaced, inwardly projecting protrusions to provide resistance to horizontal as well as vertical shear forces.

The side plates 24 are positioned in the notches 16 with the bottom edge 32 of each of the side plates engaging the bottom wall 18 of each of the notches, the outer face 26 engaging the outer side wall 22 of the notch and the inner end 38 of the base leg 34 spaced from the opposed wall 20 of the notch and defining therewith a longitudinally extending cavity.

Thereafter, as indicated by the arrow A in FIG. 4 of the drawings, an aligning force may be applied to the side plates to straighten them, if necessary, by forcing the lower portions of their outer faces against the outer side walls 22. When the notches 16 are machined the plates 12 are clamped in place. After they are machined and the plate 12 released, there may be some distortion of the plate. By applying an aligning force in the direction indicated by the arrow B, the plate 24, being rigid vertically will straighten the plate 12. The plates are then fixed in this position by, for example, the plug welds 47, the continuous weld 48 and a weld 49 between face 26 and the upper surface 14.

The continuous welds 48, as also seen in FIG. 1 of the drawings, thus fill each of the cavities defined by the inner ends of the base legs and the inner side walls of the notches with a hardenable material. The material 48 is then finished by grinding to provide a smooth flat transition surface between the upper surface of the base leg and the upper surface of the pan 12.

Because the flat upper surface 36 of the base leg projects inwardly of the form away from the curved interconnecting surface 44 the welding material 48 may be readily ground without gouging adjacent surfaces of the form. Thus, the danger of forming undercut portions which would interfere with the removal of finished slabs from the form and also form blemishes in the surface of the slabs is avoided.

It will also be noted from FIG. 1 of the drawings that a pair of cap members 50 may also be provided, mounted on the top edge 30 of each of the side plates 24 and secured thereto by a weld 52, which may be either continuous or intermittent, and an additional weld 54. The cap members 50 not only stiffen and reenforce the structure but provide flanges to facilitate handling of the forms. Further, it will be noted that the cap members 50 project outwardly over the longitudinally extending edges 56 of the base pan. This prevents excess concrete screeded from the form from accumulating on the edges of the pan.

From the above it will be apparent that the present invention provides a composite form adapted for casting relatively wide slabs without excessive transverse deflection. The finished slab must be relatively flat for purposes of appearance, since its lower surface is intended as a finished ceiling, and for structural reasons, and thus, the bottom plate or pan must be thick enough to keep deflection within acceptable limits. At the same time, considering the tensile strength of the steel and the fact that the pan must be flexed for stripping, and taking into account the depth and design details of the keyway forming protrusion 46, the thickness of the pan should not exceed a certain thickness. Thus, the thickness of the pan should be from about three-eighths inch to three-fourths inch with an optimum of approximately five-eighths inch.

While the method herein described, and the form of apparatus for carrying this method into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to this precise method and form of apparatus, and that changes may be made in either without departing from the scope of the invention.

What is claimed is:

l. A composite form comprising:

a. an elongated, substantially planar base pan,

b. means defining a pair of spaced parallel notches in an upper surface of said base pan extending longitudinally thereof,

c. each of said notches including a straight, flat bottom wall, an inner wall and a straight flat outer wall projecting upwardly from said bottom wall,

d. said bottom and outer walls defining a pair of cooperating aligning surfaces,

e. a pair of side plates each including top and bottom edges and inner and outer faces,

f. said inner faces of said side plates being machined to provide:

i. a base leg extending inwardly away from the outer face of its side plate and having a lower surface coinciding with said bottom edge of said side plate and an upper surface extending in spaced parallel relationship to said lower surface thereof,

ii. a side leg extending substantially perpendicularly with respect to said base leg and having an outer surface coinciding with said outer face of said side plate, and an inner surface extending in spaced relationship to said outer surface, and

iii. a smoothly curved portion interconnecting said upper surface of said base leg and said inner surface of said side leg,

g. means fixing said side plates on said base pan with said bottom edges received in face to face contact with said bottom wall thereof, a lower portion of said outer faces of said side plates in face to face contact with said outer side wall of said notch, and

said base legs extending inwardly of said form away from their associated curved portions and defining with said inner walls of said notches longitudinally extending cavities, and

h. a hardenable material received in said cavities with an upper surface thereof ground coplanar to said upper surfaces of said base pan and said base legs providing a smooth transition surface therebetween.

2. The form of claim 1 wherein:

a. said base leg is of substantially less thickness than said base pan, and

b. said notch is approximately equal in depth to the thickness of said base leg.

3. The form of claim 1 wherein:

a. said portions of said inner face of said side plate removed therefrom further define an inwardly projecting grout key cavity forming member.

4. The form of claim 1 wherein:

a. the radius of curvature of said smoothly curved 7 portion is from five-eighths inch to one-fourth inch.

5. The form of claim 4 wherein:

a. said radius of curvature is approximately threeeighths inch.

6. The form of claim 1 further comprising:

a. a cap member secured to an upper edge of each of said plates and projecting outwardly of said form.

7. The form of claim 6 wherein:

a. said cap members project outwardly of said form beyond longitudinal side edges of said base pan.

8. The form of claim 1 wherein:

a. said pan is from approximately three-eighths inch to three-fourths inch in thickness.

9. The form of claim 8 wherein:

a. said pan is approximately five-eighths inch in thickness.

10. A composite form comprising:

a. an elongated, substantially planar base pan,

b. means defining a pair of spaced parallel notches in an upper surface of said base pan extending longitudinally thereof,

c. a pair of solid, one piece side plates of substantial thickness relative to said base pan,

d. each of said side plates having portions removed therefrom and defining:

i. an inwardly projecting base leg having upper and lower surfaces,

ii. a side leg having inner and outer surfaces extending substantially perpendicularly with re- .spect to said base leg, and

iii. a smoothly curved portion interconnecting said upper surface of said base leg and said inner surface of said side leg,

e. said side plates being mounted on said upper surface of said base pan with said base legs received in said notches, said upper surfaces of said base legs substantially coplanar with said base pan upper surface, and inner ends'of said base legs defining with portions of said notches longitudinally extending cavities, and

f. a hardenable material received in said cavities with an upper surface thereof finished to coplanar relationship with said upper surfaces of said base legs and said base pan.

11. The form of claim 10 wherein:

a. said base leg is of substantially less thickness than said base pan, and

b. said notch is approximately equal in depth to the thickness of said base leg.

12. The form of claim 10 wherein:

a. said portions of said side plate removed therefrom further define an inwardly projecting grout key cavity forming member.

13. The form of claim 10 wherein:

a. the radius of curvature of said smoothly curved portion is from five-eighths inch to one-fourth inch.

14. The form of claim 13 wherein:

a. said radius of curvature is approximately threeeighths inch.

15. The form of claim 10 wherein:

a. said pan is from approximately three-eighths inch to three-fourths inch in thickness.

16. The form of claim 15 wherein:

a. said pan is approximately five-eighths inch in thickness.

17. A composite form comprising:

a. an elongated, relatively thick, flat base pan,

b. means defining a pair of rectangularly cross sectioned notches formed in an upper surface of said base pan and extending in spaced parallel relationship to each other longitudinally of said pan,

c. each of said notches including a bottom wall and inner and outer side walls projecting substantially perpendicularly from said bottom wall,

d. a pair of solid, one piece, relatively thick side plates having an outer face and top and bottom edges extending substantially perpendicularly with respect thereto,

e. an inner face of each of said side plates having portions removed therefrom and defining a base leg having an upper surface extending substantially parallel to said bottom edge and an inner end spaced from said outer face, a side leg having an inner surface extending parallel to said outer face, and a smoothly curved portion interconnecting said upper surface of said base leg and said inner surface of said side leg,

f. said side plates being mounted in said notches with said bottom edges engaging said bottom walls of said notches, said outer faces engaging said outer walls of said notches, and said inner ends of said base legs spaced from said inner walls of said notches and defining a pair of longitudinally extending cavities, and

g. hardenable material filling said cavities and having an upper surface thereof finished to coplanar relationship to said upper surfaces of said base pan and said base legs. 

1. A composite form comprising: a. an elongated, substantially planar base pan, b. means defining a pair of spaced parallel notches in an upper surface of said base pan extending longitudinally thereof, c. each of said notches including a straight, flat bottom wall, an inner wall and a straight flat outer wall projecting upwardly from said bottom wall, d. said bottom and outer walls defining a pair of cooperating aligning surfaces, e. a pair of side plates each including top and bottom edges and inner and outer faces, f. said inner faces of said side plates being machined to provide: i. a base leg extending inwardly away from the outer face of its side plate and having a lower surface coinciding with said bottom edge of said side plate and an upper surface extending in spaced parallel relationship to said lower surface thereof, ii. a side leg extending substantially perpendicularly with respect to said base leg and having an outer surface coinciding with said outer face of said side plate, and an inner surface extending in spaced relationship to said outer surface, and iii. a smoothly curved portion interconnecting said upper surface of said base leg and said inner surface of said side leg, g. means fixing said side plates on said base pan with said bottom edges received in face to face contact with said bottom wall thereof, a lower portion of said outer faces of said side plates in face to face contact with said outer side wall of said notch, and said base legs extending inwardly of said form away from their associated curved portions and defining with said inner walls of said notches longitudinally extending cavities, and h. a hardenable material received in said cavities with an upper surface thereof ground coplanar to said upper surfaces Of said base pan and said base legs providing a smooth transition surface therebetween.
 2. The form of claim 1 wherein: a. said base leg is of substantially less thickness than said base pan, and b. said notch is approximately equal in depth to the thickness of said base leg.
 3. The form of claim 1 wherein: a. said portions of said inner face of said side plate removed therefrom further define an inwardly projecting grout key cavity forming member.
 4. The form of claim 1 wherein: a. the radius of curvature of said smoothly curved portion is from five-eighths inch to one-fourth inch.
 5. The form of claim 4 wherein: a. said radius of curvature is approximately three-eighths inch.
 6. The form of claim 1 further comprising: a. a cap member secured to an upper edge of each of said plates and projecting outwardly of said form.
 7. The form of claim 6 wherein: a. said cap members project outwardly of said form beyond longitudinal side edges of said base pan.
 8. The form of claim 1 wherein: a. said pan is from approximately three-eighths inch to three-fourths inch in thickness.
 9. The form of claim 8 wherein: a. said pan is approximately five-eighths inch in thickness.
 10. A composite form comprising: a. an elongated, substantially planar base pan, b. means defining a pair of spaced parallel notches in an upper surface of said base pan extending longitudinally thereof, c. a pair of solid, one piece side plates of substantial thickness relative to said base pan, d. each of said side plates having portions removed therefrom and defining: i. an inwardly projecting base leg having upper and lower surfaces, ii. a side leg having inner and outer surfaces extending substantially perpendicularly with respect to said base leg, and iii. a smoothly curved portion interconnecting said upper surface of said base leg and said inner surface of said side leg, e. said side plates being mounted on said upper surface of said base pan with said base legs received in said notches, said upper surfaces of said base legs substantially coplanar with said base pan upper surface, and inner ends of said base legs defining with portions of said notches longitudinally extending cavities, and f. a hardenable material received in said cavities with an upper surface thereof finished to coplanar relationship with said upper surfaces of said base legs and said base pan.
 11. The form of claim 10 wherein: a. said base leg is of substantially less thickness than said base pan, and b. said notch is approximately equal in depth to the thickness of said base leg.
 12. The form of claim 10 wherein: a. said portions of said side plate removed therefrom further define an inwardly projecting grout key cavity forming member.
 13. The form of claim 10 wherein: a. the radius of curvature of said smoothly curved portion is from five-eighths inch to one-fourth inch.
 14. The form of claim 13 wherein: a. said radius of curvature is approximately three-eighths inch.
 15. The form of claim 10 wherein: a. said pan is from approximately three-eighths inch to three-fourths inch in thickness.
 16. The form of claim 15 wherein: a. said pan is approximately five-eighths inch in thickness.
 17. A composite form comprising: a. an elongated, relatively thick, flat base pan, b. means defining a pair of rectangularly cross sectioned notches formed in an upper surface of said base pan and extending in spaced parallel relationship to each other longitudinally of said pan, c. each of said notches including a bottom wall and inner and outer side walls projecting substantially perpendicularly from said bottom wall, d. a pair of solid, one piece, relatively thick side plates having an outer face and top and bottom edges extending substantially perpendicularly with respect thereto, e. an inner face of each of said side plates having portions reMoved therefrom and defining a base leg having an upper surface extending substantially parallel to said bottom edge and an inner end spaced from said outer face, a side leg having an inner surface extending parallel to said outer face, and a smoothly curved portion interconnecting said upper surface of said base leg and said inner surface of said side leg, f. said side plates being mounted in said notches with said bottom edges engaging said bottom walls of said notches, said outer faces engaging said outer walls of said notches, and said inner ends of said base legs spaced from said inner walls of said notches and defining a pair of longitudinally extending cavities, and g. hardenable material filling said cavities and having an upper surface thereof finished to coplanar relationship to said upper surfaces of said base pan and said base legs. 